Deep Anterior Lamellar Keratoplasty (DALK)

DALK is a partial-thickness cornea transplant procedure that involves selective transplantation of the corneal stroma, leaving the native Descemet membrane and endothelium in place. A trephine of an appropriate diameter is used to make a partial-thickness incision into the patient's cornea, followed by pneumodissection or manual dissection of the anterior stroma. This is followed by placement of a graft prepared from a full-thickness punch in which the donor endothelium-Descemet membrane complex has been removed. The intention is to preserve the patient's Descemet membrane and endothelium. Similar to PK, the graft is secured with interrupted and/or running sutures (Figure 5) and these are then selectively removed post-operatively (Figure 6).

DALK is useful for processes involving the corneal stroma in the presence of healthy endothelium. Examples include corneal ectasia (such as keratoconus in the absence of hydrops), corneal scars that are not full-thickness, and corneal stromal dystrophies (1, 15, 16).

Fig 7b: Normal anatomy is restored with reattachment of Descemet membrane to the donor stroma after placement of an air bubble in the anterior chamber.

Because it is not a full-thickness procedure, the resultant wound is stronger than that of a PK. Leaving the host endothelium intact significantly decreases the risk of endothelial rejection.

The surgery is more complex and difficult to perform than PK. If the Descemet membrane is perforated intraoperatively, the surgeon must convert to a PK. The "big bubble" technique makes dissection more consistent and is the preferred technique at our institution (12).